The present invention relates generally to prosthetic devices and, more particularly, to an interface connector for coupling prosthetic limb pylon or shaft components to a prosthetic limb socket component.
A prosthesis is often used to replace an amputated portion of a limb and to help restore the amputee's ability to use that limb. A prosthesis for a lower extremity amputation will often include an artificial foot connected to a upright assembly (pylon, tube or shaft) which is in turn connected to a custom fitted socket assembly (it is also known in the field to use non-custom fitted socket assemblies). If the amputation is an above-the-knee amputation, the upright assembly will commonly include an artificial knee joint.
An above-the-knee prosthesis typically requires two interlaying sockets; an inner socket consisting of a flexible, thermoplastic material, and a stronger, less flexible outer socket which is attached to the upright assembly of the prosthesis. The inner socket is typically designed to interface with and cushion the amputee's residual limb, to protect the amputee's residual limb from the interconnection components which attach the socket assembly to the upright assembly, and to provide an air-tight seal between the residual limb and the outer socket.
The outer socket is typically made from a hard thermoplastic material. The outer sockets can be created by heating a thermoplastic preform cone, stretching the heated cone over a positive cast of the amputee's residual limb, and then vacuum forming the cone in place over the positive cast. Alternatively, the outer socket can be fabricated by heating an extruded sheet of thermoplastic and wrapping the sheet over the positive cast; or by a laminating process using a fiber reinforced, thermal set plastic. Often times, interconnection components, such as an attachment plate, for coupling the outer socket to the upright assembly components of the prosthesis, will be permanently molded into the thermoplastic outer socket during the vacuum forming operation. Alternatively, the interconnection components may be permanently laminated into the socket.
Several disadvantages are inherent in these above-the-knee prosthetic devices. The combination of the inner socket, the interconnection components, and the outer socket give the prosthesis a long profile. Therefore, if the amputation is immediately above the knee, the prosthesis may extend the thigh beyond where the knee joint should be. Also, in preparing a positive cast for fabricating the outer socket, the thickness of the distal end of the positive cast is difficult to predict because the inner socket, the interconnection components, and the outer socket provide three levels of variance. This can lead to unpredictable dimensions in the socket assemblies. Furthermore, because the interconnection components are permanently attached into the socket assemblies, if a new socket is desired, the entire socket assembly including the interconnection components will have to be re-fabricated, and the socket and interconnection components of the old prosthesis will then be discarded.
Typically, a below-the-knee prosthesis will include an inner, soft insert material for interfacing with the amputee's residual limb, a set of interconnection components, and the outer socket. To fabricate the outer socket for this device a positive cast of the amputee's residual limb will be made, and then a layer of insert material, representing the thickness of the socket's inner insert material, will be formed over the cast. To account for the thickness of the interconnection components and to obtain proper alignment between the socket and the upright assembly, multiple layers of the insert material must be added to the distal end of the positive cast and then these layers must then be planed down to the precise angle and dimensions required. A disadvantage with this process is that it is very time consuming and requires much skill and equipment to accomplish.
Another disadvantage with typical below-the-knee prosthetic devices is that as the amputee's residual limb changes shape or size (as will often occur), the socket components will have to be replaced. Because the interconnection components are usually permanently molded into the sockets, the entire socket including the interconnection components will have to be refabricated, and the socket and interconnection components of the old prosthesis will then be discarded.
Accordingly, a need exists for improved prosthesis components which reduce the amount of skill, time, and equipment needed to fabricate or replace a prosthesis. A need exists for interface components which reduce the levels of variance in the socket fabrication processes. A need exists for interface components which reduce the longitudinal profile of the socket assemblies. Furthermore, a need exists for prosthesis components which facilitate the automation of the prosthesis fabricating process.